The key goal in clinical transplantation is the induction of donor-specific transplantation tolerance to minimise the morbidity and mortality associated with long-term immunosuppression. Naturally occurring CD4(+)CD25(+) regulatory T cells (Tregs) expressing forkhead transcript factor FoxP3 play a crucial role in the prevention of autoimmunity, and appear to mediate transplantation tolerance, and these cells can have indirect allospecificity for donor antigens. Here we show that self-reactive human CD4(+)CD25(+) Tregs can be subverted into allopeptide-specific cells in vitro and be expanded to large cell numbers, and that similar in vitro expanded murine CD4(+)CD25(+) Tregs with indirect allospecificity were capable of inducing donor-specific experimental transplantation tolerance. These data provide a platform for clinical studies using CD4(+)CD25(+) Tregs with indirect allospecificity as potential reagents for the induction of donor-specific transplantation tolerance.